Aluminum and other metals, such as lead, magnesium, zinc, zirconium, titanium and silicon may be produced via electrolysis. With respect to aluminum, alumina dissolved in molten fluoride bath is electrolyzed at temperature of from about 900° C. to about 1000° C. to produce aluminum metal.
One conventional system for producing aluminum is illustrated in FIG. 1. A conventional potline 10 includes a plurality of aluminum electrolysis cells 12. Each of these electrolysis cells 12 produces aluminum metal via conventional electrolytic processes. During metal production, the electrolysis cells 12 produce fumes, generally referred to as off-gases (OG), which are sent to a gas treatment center 20.
The off-gases (OG) generally include gaseous fluoride (e.g., HF) and bath fines (BF), which contain NaAlF4. Gaseous fluoride is readily removed from the off-gases (OG) by contacting it with fresh alumina (FA) in the gas treatment center 20 (e.g., via use of a dry scrubber) to produce reacted alumina (RA), which is then sent back to the potline 10 for use as a feed stream to the electrolysis cells 12.
The off-gases (OG) may include other elements, such as, Fe, S, P, Ti, V and Ga, to name a few, which are often associated with small carbon particles contained in the off-gases, generally referred to as carbon fines (CF). The carbon fines (CF) may cause impurity build-up in the electrolysis cells if recycled to the potline 10. Furthermore, in the gas treatment center 20, alumina fines (AF) may be produced due to the feed of the fresh alumina (FA) to the gas treatment center 20. If transported to the electrolysis cells 12, these alumina fines (AF) may cause lower current efficiency in the electrolysis cells 12. Due to the size of the alumina, carbon and bath fines, which generally have an average diameter of not greater than about 20 microns, collection and treatment of these particulate fines is problematic.